Latest Nov 2, 2008 Gallup Poll
Check out Gallup numbers in the last two elections:
In 2000, The poll shows Bush +2. The actual was Gore +.5. So it was about 2.5% off.
In 2004, the poll shows Bush/Kerry even. The actual was Bush +2. So the poll was again off by 2%. Both are obviously within the margin of error.
The most famous Gallup screw up was the Truman/Dewey in 1948. But the story there strangely was that the last poll was in mid-October. The poll was famously off by 5%.
BUT!!!!!! - Obama is up in the traditional likely voter polls by 11% traditional likely and 13% among registered voters.